An adjunct to assist cardiopulmonary resuscitation (CPR) might improve the quality of CPR performance.This study was conducted to evaluate whether a simple audio-visual prompt device improves CPR performance by emergency medical technicians (EMTs).From June 2008 to October 2008, 55 EMTs (39 men, mean age 34.9±4.8 years) participated in this study. A simple audio-visual prompt device was developed. The device generates continuous metronomic sounds for chest compression at a rate of 100 beats/min with a distinct 30 th sound followed by two respiration sounds, each for 1second. All EMTs were asked to perform a 2-min CPR series on a manikin without the device, and one 2-min CPR series with the device.The average rate of chest compressions was more accurate when the device was used than when the device was not used (101.4±12.7 vs. 109.0±17.4/min, respectively, p=0.012; 95% confidence interval [CI] 97.2–103.8 vs. 104.5–113.5/min, respectively), and hands-off time during CPR was shorter when the device was used than when the device was not used (5.4±0.9 vs. 9.2±3.9 s, respectively, p<0.001; 95% CI 5.2–5.7 vs. 8.3–10.3 s, respectively). The mean tidal volume during CPR with the device was lower than without the device, resulting in the prevention of hyperventilation (477.6±60.0 vs. 636.6±153.4mL, respectively, p<0.001; 95% CI 463.5–496.2 vs. 607.3–688.9mL, respectively).A simple audio-visual prompt device can improve CPR performance by emergency medical technicians.